Abstract: This paper aims at the requirements of an automobile engine cylinder block processing line, a fixture is designed to overcome the problem of clamping and compression deformation in actual processing. A special processing method is adopted, combined with suitable parameter index settings, to avoid workpiece deformation, and the feasibility and effectiveness of the method were verified during processing, and all the processing procedures were completed in line with the production line rhythm. This article briefly describes the current situation of automobile engine cylinder block production, production line equipment composition, production line process plan, OP20 fixture design, trial cutting verification and other contents.